1. a white fatty substance that forms a medullary sheath around the axis cylinder of some nerve fibers • Syn: myelin, myeline • Derivationally related forms: myelinic (for: myelin) • Hypernyms: fat • Substance Holonyms: medullary sheath, myelin sheath 2. lower or hindmost part of the brain; continuous with spinal cord; ('bulb' is an old term for medulla oblongata) - the medulla oblongata is the most vital part of the brain because it contains centers controlling breathing and heart functioning • Syn: medulla oblongata, bulb • Derivationally related forms: bulbar (for: bulb), medullary • Hypernyms: neural structure • Part Holonyms: brainstem, brain-stem, brain stem • Part Meronyms: respiratory center 3. the inner part of an organ or structure in plant or animal • Ant: cortex • Derivationally related forms: medullary • Hypernyms: animal tissue, plant tissue • Hyponyms: adrenal medulla
